Hammerhead has just released one of their larger, monthly software updates, this time there is integration with Shimano Di2 and Garmin Varia. (v1.95.686.3)
The Di2 capabilities on the Karoo vary depending on the exact components you have. Di2 can just be shifting but the higher-end shifters also have buttons on top of the hoods which can trigger events on the Karoo such as taking a lap, changing screens or zooming in on a graph…Di2 is not just about changing gears, it can be a VERY useful addition to avoid using a touchscreen whilst riding. Ideal for the Karoo.
Garmin Varia are lights but they are also a pretty cool safety device as they include a car sensing radar – you have to have used one to believe me when I say it’s good! The Karoo then displays a small graphic showing the proximity of cars to your rear.
Return to the main Hammerhead Karoo Review
Shimano Di2
The Karoo now integrates with Di2 shifting when enabled by a Shimano inline wireless unit such as the EW-WU111.
The Karoo now supports:
- Pairing Di2 Electronic Shifter Systems with the Karoo
- Shifting-related data fields:
- Electronic Shifting Battery Level
- Electronic Shifting Current Gears Selected
- Electronic Shifting Single Data Field Gears Selected
- Electronic Shifting, Number of Shifts
- Graphical Data Field: Electronic Shifting (Index) Current Gears Selected
I’ve shown those fields here on the Karoo. The first image is a pretty cool climbing screen with your upcoming elevation profile, power output in watts and proof that you have no more gears left to use 😉 the second image just shows the Di2 data fields and, in reality, I doubt you’d have a single screen set up like that.
Navigating the Karoo via Di2 Hood Buttons is also supported but not all Di2 shifters have these buttons, more here
-
- Tap to swipe Screens Left/Right (Karoo Buttons “B” and “C”)
- Double-tap left to access “Lap” (Karoo button “E”)
- Double-tap right to access “Menu” (Karoo button “D”)
- Long press left to zoom in (like long-press “B”)
- Long press right to zoom out (like long-press “C”)
Riders are able to change the Di2 shift mode between Manual, S1, and S2 modes in the detail page for the sensor
SRAM & ETap are now also compatible with
Garmin Varia Radar
Support for Varia RADAR added and covers Varia 500 and Varia 510
Other than no sound, it works REALLY well on the Karoo. The display interface is MUCH better than Garmin’s.
- A bar is enabled to the left of the screen when there is a threat condition. you can see in the images below that the bar changes colour depending on the status of the threat and the bar has an icon for what it deems to be approaching vehicles
- Hammerhead claim to be able to reliably display 2 cars (Varia supports up to 8 and, in my experience, the Hammerhead correctly displayed 4 approaching vehicles)
- Sensors can be (un-)muted
More Features
- The capability of Karoo and Dashboard maps have been updated to show points of interest (POI) when imported from RideWithGPS. For now, all POIs are read-only and all types are shown with a common graphic indicator (pin).
- The turn-by-turn banner colours were changed for visibility and to leave red open for more consistent use on the Karoo
- The feature menu (shown with the “D” button in the ride) was simplified to remove the minimized view
- Several bug fixes
Return to the main Hammerhead Karoo Review
Last Updated on 20 January 2026 by the5krunner
My favourite kit and nutrition
- Injinji – Runners protect your toes. Avoid discomfort and minor injury. Run more. Run faster. I use them.
- Garmin 90-degree charging adapter — The small adapter that keeps your charging cables tidy. Essential for race day. I use one.
- Garmin charging puck — the fastest and most reliable way to top up your Garmin before a session. I use one.
- Ravemen FR300 — Front light that mounts directly under your Garmin or Wahoo head unit. Keeps your bars clean and your beam pointed where it matters. I use one.
- Body Glide – The blue anti-chafe stick that all swimmers and many runners use. I use it.
- Maurten — The race nutrition trusted by elite athletes. Gels and drink mixes engineered to be easy on the stomach. I use them.
- Garmin Varia RTL515 — A radar rear light that alerts you to vehicles approaching from behind. Pairs with your Edge or Garmin watch. I use this model.
- Favero Assioma Pro RS2 — The power-meter pedals most serious cyclists choose. Accurate, easy to move between bikes. I use this model.
- Garmin Forerunner 970 — A serious choice for a pro-grade triathlon watch. I use this.
- Polar H10 — My daily driver for accurate, waking HRV readings.
- Wahoo ELEMNT Roam 3 — The bike computer that has the feature Garmin lacks: usability. I use mine on most rides.
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tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors. ID
